There are many reasons why it is desirable for a structure to be in a panel form, and for example, a building or other structure may comprise a plurality of "modules" which are secured together. For example, in the erection of a wall or ceiling of a building, it is most desirable that the walls or ceilings comprise panels which are readily and inexpensively interengaged with one another so as to avoid expensive "on site" work, and in order to achieve this, it is in turn desirable that interengaging means be readily assembled within a panel itself. If a louvre panel is required, it is desirable that the louvre panel should also be in the form of a sub-assembly which can be secured to a building or other structure.